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Title: RE-EXAMINING CURRENT QUESTIONS OF WHEAT LEAF APPEARANCE AND TEMPERATURE PROCEEDINGS OF THE MAIZE AND WHEAT SYSTEMS MODELING WORKSHOP APRIL, 2001.

Author
item McMaster, Gregory
item HUNT, L - UNV. OF GUELPH, CANADA

Submitted to: CIMMYT Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/23/2001
Publication Date: 12/1/2003
Citation: Mcmaster, G.S., Hunt, L.A. 2003. Re-examining current questions of wheat leaf appearance and temperature. Proceedings of the maize and wheat systems modeling workshop, April 23-25, 2001. CIMMYT, Natural Resources Group, Geographic Information Systems Series 03-01, pp. 18-22.

Interpretive Summary: For many reasons, the rate of leaf appearance (or the phyllochron) is important in understanding and simulating canopy development, structure, and dynamics. Many factors influence the phyllochron of wheat (Triticum aestivum L.), but the most important factor is temperature. The paper discusses two important questions currently be asked by scientists: "Is leaf appearance rate linear with temperature?" and "Where do measure temperature for predicting leaf appearance?". While the temperature response across the entire temperature range that leaves normally appear is clearly non-linear, there is a linear region, and this has contributed to some of the confusion of linear vs. non-linear. Other confounding factors that have lead to the confusion are that both during and across days, the temperatures when leaves are produced normally are within the linear region, but often can fluctuate beyond the linear phase, cultivars can vary yslightly in their temperature response, and temperature interacts with other factors. While measuring the phyllochron response to temperature may be largely a physics problem, it is complicated by knowing where to measure the temperature since the meristematic region covers a significant distance and temperature in other parts of the plant will affect secondary factors that influence the phyllochron.

Technical Abstract: The rate of leaf appearance, or the phyllochron, is critical in simulating canopy development, structure, and dynamics. Many factors can influence the phyllochron of wheat (Triticum aestivum L.), but the most important factor is temperature. This paper explores some current questions of the complicated relationship between wheat leaf appearance and temperature. Specifically, the questions of whether the phyllochron is linearly related to temperature and what is the site of temperature perception are addressed. While the temperature response across the entire temperature range clearly is non-linear, there is a linear region, and this has contributed some confusion. Additional confounding factors are that both during and across days, temperatures when leaves are produced normally are within the linear region, but often can fluctuate beyond the linear phase, cultivars can vary slightly in their temperature response, and temperature interacts with other factors. While measuring the phyllochron response to temperature may be largely a physics problem, it is complicated by knowing where to measure the temperature since the meristematic region covers a significant distance and temperature in other parts of the plant will affect secondary factors that influence the phyllochron.